1. Field
The present disclosure relates generally to orthopedic medical devices, and more specifically to input pointing devices and assisted navigation surgical tools.
2. Introduction
Input pointing devices permit pointing to a point of interest. Within a navigation system its utility is a function of the sensing technology. An optical camera system generally processes captured images to determine the pointed location. An electromagnetic system generally evaluates changes in magnetic field strength. An ultrasonic sensing system evaluates received ultrasonic waveforms.
As one example, an optical navigation system can be used for a knee replacement surgery. A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material and prosthetic components. The knee is a hinge which provides motion at the point where the femur meets the tibia. During a total knee replacement, the distal end of the femur bone is removed and replaced with a femoral component. The proximal end of the tibia is also removed and replaced with a tibial component. Depending on the condition of the kneecap portion of the knee joint, a button may also be added under the kneecap surface.
During total knee replacement surgery it is imperative that the bone cuts on the femur and tibia are made to result in proper alignment. The alignment ensures proper balance and straightness of the leg. The bone cuts can be made with use of physical guides and jigs, and more recently, by way of highly accurate computer assisted systems. Commercial CAS systems are based on specific sensing principles (e.g., active or passive optical or electromagnetic) where precise intra-operative orientation is provided by high-resolution imaging techniques (e.g., computed tomography (CT), magnetic resonance imaging (MRI)). These systems generally require the placement of fiducial markers, CT or MRI imaging, data transfer to the operating room (OR), and identification and registration of the fiducials. They are also sensitive to deviations in light intensity, contrast, and reflections. When performing these preparatory and practice steps, each platform has individual needs and a number of potential deficiencies influencing the accuracy of the system.
CAS platforms generally consist of three main parts: a computer workstation, a position interface (e.g., camera system) and a passive instrument pointer. The computer workstation is the hub between the position interface and the instrument pointer. It is generally positioned away from the surgical area yet close enough to track the instrument pointer. Although it requires minimal space in the Operating Room and is sufficiently mobile it is generally a capital expense that is maintained on-site. The instruments must be sterilized with each use and the sophisticated optical components are custom made.